Render comprising honeycomb and cementitious or clay or geopolymer material

ABSTRACT

A render layer for a building comprises a honeycomb core of nonwoven polypropylene web, and a cementitious material fully filling the cells of the core, wherein (i) the nonwoven web has a porosity of from 5 microns to 600 microns, (ii) the core has a cell size of from 5 mm to 200 mm, (iii) the expansion and contraction across the plane of the core is greater than the expansion and contraction of the cementitious material filling the cells of the core, and (iv) the cementitious material is partly impregnated into the cell walls of the core.

BACKGROUND 1. Field of the Invention

This invention pertains to the field of building construction and, inparticular, to reinforced crack-resistant render.

2. Description of Related Art

Cementitious materials are known to be fragile while under tensile load.The traditional solution to this problem is to reinforce the cement likematrix with rigid materials having high tensile strength and highmodulus. In the construction field, steel bars are known to reinforceconcrete matrix for structural parts. Another approach is to use a fiberglass net or grid to reinforce the render layer. A disadvantage of usingsuch a grid is a tendency for the render to crack caused by the badpositioning of the grid. Further, resistance to shock perpendicular tothe plane of the render is not optimal. There remains a need to reduceor eliminate the extent of render cracking in a building structurecaused by strain in the render. This strain may be caused by contractionduring curing of the render or by thermal expansion of the cured render.

Japanese publication JP11336249 discloses a thermal insulation andacoustic-proof wall panel structure for outer walls of buildings thathas honeycomb panels in which mortar is filled into the cell walls ofthe honeycomb but not to fully fill the cell walls. The honeycomb ismade from ceramic, aluminum or paper.

SUMMARY OF THE INVENTION

This invention pertains to a render layer for a building comprising

(i) a honeycomb core of nonwoven polypropylene web, and

(ii) a cementitious or clay or geopolymer material fully filling thecells of the core,

wherein

(a) the nonwoven web has a porosity of from 5 microns to 600 microns,

(b) the core has a cell size of from 5 mm to 200 mm, and

(c) the expansion and contraction across the plane of the core isgreater than the expansion and contraction of the cementitious or clayor geopolymer material filling the cells of the core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are representations of views of a hexagonal shapedhoneycomb.

FIG. 2 is a representation of another view of a hexagonal cell shapedhoneycomb.

FIG. 3 is an illustration of a cladding structure on a building wall.

DETAILED DESCRIPTION Render Layer

The render layer for a building comprising a honeycomb core of nonwovenpolypropylene web, and a cementitious material fully filling the cellsof the core,

Honeycomb Core

FIG. 1A is a plan view illustration of one honeycomb 1 of this inventionand shows cells 2 formed by cell walls 3. FIG. 1B is an elevation viewof the honeycomb shown in FIG. 1A and shows the two exterior surfaces,or faces 4 formed at both ends of the cell walls. The core also hasedges 5. FIG. 2 is a three-dimensional view of the honeycomb. Shown ishoneycomb 1 having hexagonal cells 2 and cell walls 3. The “T” dimensionor the thickness of the honeycomb is shown in FIG. 2. Hexagonal cellsare shown, however other geometric arrangements are possible withsquare, trapezoidal, over-expanded and flex-core cells being among themost common possible arrangements. Such cell types are well known in theart and reference can be made to Honeycomb Technology by T. Bitzer(Chapman & Hall, publishers, 1997) for additional information onpossible geometric cell types.

The core has a cell size of from 5 to 200 mm, preferably from 5 to 50 mmand more preferably from 11 to 22 mm. The cell size is the diameter ofan inscribed circle within the cell of the core that touches at leasttwo cell walls.

In one embodiment, the core comprises a nonwoven polypropylene webhaving a porosity of from 5 microns to 600 microns. In anotherembodiment, the core comprises a nonwoven polypropylene web having aporosity of from 10 microns to 500 microns or even 80 to 120 microns. Byporosity is meant the Apparent Opening Size (AOS) O₉₅ as measuredaccording to ASTM D4751-12. If the web porosity is less than 5 micronsthe cementitious material does not penetrate into the nonwoven web andthus there is no effective bond between those two materials. If the webporosity is greater than 600 microns the cementitious material canpenetrate fully into the web and the cell walls lose its spring effecti. e. the ability of the cell walls to expand or contract. The core canbe of any desired thickness but core thicknesses of from 5-12 mm areparticularly useful.

It is a requirement of this invention that the expansion and contractionacross the plane of the core is greater than the expansion andcontraction of the cementitious material filling the cells of the core.In some embodiments the expansion and contraction across the plane ofthe core is at least 10% greater than the expansion and contraction ofthe cementitious material filling the cells of the core.

Cementitious Material

Cementitious material is a component of the render layer. Suitablecementitious materials include plaster, mortar or concrete. In otherembodiments, the cementitious material may include mineral or a binder.The render may be organic or mineral in nature. In some embodiments, anorganic render is preferred. Renders of clay or geopolymer concrete arealso suitable materials. Typically a geopolymer concrete ischaracterized by long chains or networks of inorganic molecules.

The filled core structure may be produced by dispensing the wetcementitious material over the core so as to fill the cell wallsfollowed by scraping off surplus cement or by placing the core into awet slab of cement or by a combination of both. The cementitiousmaterial is then allowed to cure (set). In a preferred embodiment, thecementitious material fully fills the cells of the core.

Preferably the cementitious material is partly impregnated into the cellwalls of the core. This partial impregnation, which is facilitated bythe selected porosity of the web material, provides enhanced cohesiveadhesion between the core and the cementitious material without the needfor additional binding agents.

The greater expansion characteristics (dilatation capability) across theplane of the core when compared to the expansion characteristics of thecementitious material prevents micro-cracking of the render.

Cladding Structure

FIG. 3 is a schematic of a composite cladding structure for a buildingwall, comprising in order

(i) an insulation layer,

(ii) the render layer of claim 1, and

(iii) at least one decorative layer,

wherein the insulation layer is affixed to the building wallmechanically and/or with adhesive.

In FIG. 3, the building wall is shown as 31, the insulation layer as 33,the render (honeycomb core filled with cementitious material) layer as34 and the at least one decorative layer is 35. For purposes of clarity,the figure is shown in a partly exploded view and the render is notshown inside the cells of the core.

Exemplary means of mechanically fixing the insulation layer to thebuilding wall include bolts, nails, pins, screws, or staples. Exemplaryadhesive materials for fixing the insulation layer to the building wallare liquids, films, powders or pastes. In some embodiments the adhesivemay be supported by a lightweight scrim. An example of an adhesive bondis shown as 32 in FIG. 3.

Examples of insulation materials are glass, aerogel or mineral fiberbatts and foam such as expanded polystyrene or polyurethane foams.

Typically, the decorative layer is a thin render layer which is organicin nature, is pigmented and may optionally contain some hydrophobicagents. However, other materials may sometimes be used.

The compressive resistance of the honeycomb core helps to reduce impactdamage to a cladded structure.

Test Methods

Experimental samples were tested according to the protocol of ETAG 004,Edition 2000, Amended February 2013—External Thermal InsulationComposite Systems (ETICS) with Rendering. Two types of evaluation werecompleted (i) weathering in a climatic chamber to observe microcrackingduring curing and (ii) a shock or impact test with 10 Joules of energyfrom a 63.5 mm steel ball dropped from a height of 1.02 m (ISO 7892issued 1998).

EXAMPLES Shrinkage Evaluation

The render was a mineral material SM700 available from Knauf Insulation,Shelbyville, Ind.

The render was poured to fully fill the cells of the core and allowed toharden. All examples were left for 30 days after pouring of the renderin ambient conditions to allow shrinkage to develop. The temperaturesgenerally ranged from 17 to 22 degrees C. although temperature drops toas low as 14 degrees C. occurred at weekends when the heating was turnedoff. Relative humidity was between 25 to 43% with one spike at 55%.Shrinkage was evaluated in the long and short directions of thetrapezoidal shaped cells.

Comparative Example A

This example comprised a 10 mm thick slab of render without honeycombcore or any other reinforcement material.

Comparative Example B

This comprised a 10 mm thick slab of render having a backing offiberglass net type Gittex (mesh size 5 mm) from Knauf.

Example 1

The core was made from 190 gsm Typar® polypropylene sheet available fromE. I. DuPont de Nemours and Company, Wilmington, Del. The core thicknesswas 10 mm. The cell shape approximated to a trapezoidal shape with alongest dimension of about 17 mm and a shortest dimension of about 12mm. This gave a core that was more rigid in one direction, the longdirection.

The core was filled to the top with render.

All examples showed continued shrinkage for the first three days with nofurther deterioration during the remaining 27 days of the evaluation.This latter level is referred to as the Steady State Shrinkage which ispresented in Table 1.

TABLE 1 Steady State Example Shrinkage (microns) Comparative A 7500Comparative B 3700 Example 1 3200 (long direction) Example 1 4250 (shortdirection)

The results showed that the incorporation of a honeycomb structure intocementitious material as in Example 1 gave a product that significantlyreduced the shrinkage of the render when compared to the honeycomb-freerender of Example A and was comparable to that of the fabric backedrender of Example B. This demonstrates the use of honeycomb having a webporosity as defined above to control shrinkage during curing of thecementitious material.

Impact Evaluation

Two series of test were carried out to evaluate impact resistance. Thefirst series of tests were Comparative Examples C and D and inventiveExamples 2-5. In all these examples the render was SM 700. All theexamples were tested for impact resistance by measurement of residualdeformation and a visual observation as to the extent of cracking. Allexamples were prepared on a 1 m×0.5 m expanded polystyrene (EPS) platethat was 50 mm thick unless indicated otherwise. The EPS plate forComparative Examples A-B and Examples 3-5 was placed in a metal framerepresentative of a window frame.

All samples were placed in a climatic chamber at 20 degrees C. and 50%relative humidity for 4 weeks to allow full curing of the cementitiousmaterial. The samples were then tested for impact resistance.

Comparative Example C

This consisted solely of a layer of a nominal 7 mm thick layer of SM700render.

Comparative Example D

This example was a 7 mm thick fiberglass net type Gittex (mesh size 5mm) from Knauf that was fully impregnated with SM700 render.

Example 2

This sample comprised a 7 mm thick core having a cell size of 11 mm madefrom 150 gsm Typar® polypropylene sheet. The core was filled with SM700render.

Example 3

This was as Example 2 except that there was a 1 mm thick SM700 renderlayer on one outer surfaces of the core.

Example 4

This was as Example 3 except that the 1 mm thick render layer was afinishing render of SKAP 1.7 mm grain from Knauf.

Example 5

This was as Example 2 except that there was an additional 1 mm thickfinishing render layer of SKAP 1.7 mm grain from Knauf on top of the 1mm thick SM700 render layer.

The results of the impact test are shown in Table 2. All samples crackedafter impact.

TABLE 2 Residual Deformation Sample (mm) Comparative C 4.8 Comparative D3.4 Example 2 3.6 Example 3 4.4 Example 4 5.0 Example 5 3.4

All the deformation values showed a relatively deep ball penetration andwere considered to be statistically similar showing that the honeycombcontaining examples performed no worse than the comparative examples.

The second series of tests were inventive Examples 6-16. All of theseexamples had core made from 190 gsm Typar® polypropylene sheet. The corethickness was either 7 mm or 10 mm and the cell size was 11 mm. Therenders filling the core cells were both organic renders either typeZF-SIL 3585 from Brillux GmbH, Muenster, Germany or Plastol P394 fromKnauf. In some examples there was also a 3 mm thick fiberglass net ontop of the render filled core. In some other examples there was also adecorative layer as an outer surface. The decorative material was eitherRausan KR K#3517 from Brillux or SKA P311 from Knauf.

The results are summarized in Table 3.

TABLE 3 Core EPS Total Residual Thickness Thickness Glass Deco thicknessDeformation Example (mm) (mm) Render Layer Layer (mm) (mm) 6 10 10Brillux Yes Rausan 14 2.2 7 10 10 Brillux Yes Rausan 14 2.4 8 10 10Brillux Yes Rausan 14 2.1 9 10 50 Brillux Yes Rausan 14 2.0 10 10 50Brillux Yes Rausan 14 3.0 11 7 50 Brillux No Rausan 8 2.8 12 7 50Brillux No Rausan 8 2.2 13 10 50 Pastol No Skap 11 3.0 14 10 50 PastolNo Skap 11 2.7 15 7 50 Pastol No Skap 8 1.7 16 7 50 Pastol No Skap 8 2.6

The residual deformation of all Examples 6-16 was lower than thosereported in Table 2. Further, none of the samples had cracks as a resultof the impact.

What is claimed is:
 1. A render layer for a building comprising (i) a honeycomb core of nonwoven polypropylene web, and (ii) a cementitious or clay or geopolymer material fully filling the cells of the core, wherein (a) the nonwoven web has a porosity of from 5 microns to 600 microns, (b) the core has a cell size of from 5 mm to 200 mm, and (c) the expansion and contraction across the plane of the core is greater than the expansion and contraction of the cementitious or clay or geopolymer material filling the cells of the core
 2. The render layer of claim 1 wherein the honeycomb core has a cell size of from 5 mm to 50 mm.
 3. The render layer of claim 1 wherein the cementitious material comprises plaster, mortar, concrete, mineral or organic binder.
 4. The render layer of claim 1 wherein the nonwoven web has a porosity of from 80 microns to 120 microns.
 5. The render layer of claim 1 wherein the expansion and contraction across the plane of the core is at least 10% greater than the expansion and contraction of the cementitious material filling the cells of the core.
 6. The render layer of claim 1 wherein the cementitious or clay or geopolymer material is partly impregnated into the cell walls of the core.
 7. The render layer of claim 2 wherein the honeycomb core has a cell size of from 11 mm to 22 mm.
 8. A composite cladding structure for a building wall, comprising in order (i) an insulation layer, (ii) the render layer of claim 1, and (iii) at least one decorative layer, wherein the insulation layer is affixed to the building wall mechanically and/or with adhesive. 